U.S. patent number 5,302,945 [Application Number 07/934,599] was granted by the patent office on 1994-04-12 for electric appliance fault monitor and indicator.
This patent grant is currently assigned to Technimedics Corporation. Invention is credited to Kevin J. Stoltenberg.
United States Patent |
5,302,945 |
Stoltenberg |
April 12, 1994 |
Electric appliance fault monitor and indicator
Abstract
A monitor and indicating circuit for an electric appliance
detects the absence of the energization voltage for the appliance
exceeding a predetermined threshold and provides a brilliant flash
from a xenon lamp which is visible from great distances. The
circuitry is contained within a sealed housing and includes a
self-contained battery supply and attachable to a fence post. The
circuit employed is specifically designed to conserve battery power
by controlling the flash frequency and the charging time for the
storage capacitor used with the xenon flash tube.
Inventors: |
Stoltenberg; Kevin J.
(Clitherall, MN) |
Assignee: |
Technimedics Corporation
(Clitherall, MN)
|
Family
ID: |
25465779 |
Appl.
No.: |
07/934,599 |
Filed: |
August 24, 1992 |
Current U.S.
Class: |
340/660; 324/133;
340/659; 256/10; 340/648; 340/564 |
Current CPC
Class: |
A01K
3/005 (20130101); G08B 13/122 (20130101); G01R
31/382 (20190101); G08B 21/185 (20130101); G01R
31/3646 (20190101) |
Current International
Class: |
A01K
3/00 (20060101); G01R 31/36 (20060101); G08B
21/20 (20060101); G08B 21/00 (20060101); G08B
13/12 (20060101); G08B 13/02 (20060101); G08B
021/00 () |
Field of
Search: |
;340/564,657,658,659,660,648 ;256/10 ;324/122,133 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hofsass; Jeffery A.
Attorney, Agent or Firm: Haugen and Nilolai
Claims
What is claimed is:
1. Apparatus for monitoring the voltage applied to an electrical
appliance and for visually signalling a drop in said voltage below
a predetermined acceptable threshold to a location remote from said
appliance comprising, in combination:
(a) means electrically coupled to a voltage supply for said
appliance for sensing when the amplitude of the voltage from said
voltage supply has fallen below said predetermined acceptable
threshold;
(b) a power source independent and electrically isolated from said
appliance voltage supply; and
(c) xenon flash lamp means operatively coupled to said means for
sensing and to said independent power source for providing an
intense flash of light visible at great distances at predetermined
intervals, so long as the amplitude of the voltage of said voltage
supply remains below said predetermined acceptable threshold.
2. Apparatus for visually signalling malfunctioning of an electric
fence having posts, said electric fence being of the type in which
at least one continuous length of fence wire is strung between post
mounted insulators and is periodically energized by high voltage
pulses generated by a fence voltage supply capable of administering
a non-lethal shock to animals coming into contact therewith, the
combination comprising:
(a) means affixed to ones of said posts at predetermined intervals
along the fence line for sensing when the amplitude of said high
voltage pulses has fallen below a predetermined acceptable
threshold;
(b) a power source independent and electrically isolated from said
fence voltage supply; and
(c) xenon flash lamp means operatively coupled to said means for
sensing and to said independent power source for providing an
intense flash of light visible at great distances at predetermined
intervals so long as the amplitude of said high voltage pulses
remains below said predetermined acceptable threshold.
3. The apparatus as in claim 2 wherein said means for sensing
comprises:
(a) inductive pick-up coil coupled to said fence wire;
(b) means coupled to said pick-up coil for detecting the absence of
said high voltage pulses exceeding said predetermined threshold for
a predetermined time interval and for producing a control signal
indicative of such condition; and
(c) means responsive to said control signal for triggering said
xenon flash means.
4. The apparatus as in claim 2 wherein said means for sensing
comprises:
(a) a resistive voltage divider having a plurality of series
connected resistors of predetermined ohmic value having first and
second terminals and a plurality of selectable taps therealong,
said first terminal being connected to said fence wire and said
second terminal being grounded, with one of said selectable taps
establishing said predetermined threshold;
(b) means coupled to said one of said selectable taps for detecting
the absence of said high voltage pulses exceeding said
predetermined threshold for a predetermined time interval and for
producing a control signal indicative of such condition; and
(c) means responsive to said control signal for triggering said
xenon flash means.
5. The apparatus as in claim 3 or 4 wherein said xenon flash lamp
means comprises:
(a) a xenon flash lamp having a pair of input terminals and a
control terminal;
(b) a storage capacitor connected to said pair of input terminals
in parallel with said xenon flash lamp;
(c) battery operated means for developing a high dc voltage on said
storage capacitor; and
(d) means, including said means for triggering, responsive to said
control signal for periodically applying an ionizing potential to
said control terminal of said xenon flash lamp to thereby effect
the discharge of said storage capacitor through said xenon flash
lamp.
6. The apparatus as in claim 5 wherein said battery operated means
comprises:
(a) a dc battery;
(b) a step-up transformer having a primary winding and a secondary
winding;
(c) a semiconductor switching means connected in series with said
dc battery and said primary winding and having a control
terminal;
(d) current rectifying means connected in series with said
secondary winding and said storage capacitor; and
(e) oscillator means coupled to said control terminal of said
semiconductor switching means for rendering said semiconductor
switching means conductive and non-conductive at a predetermined
frequency.
7. The apparatus as in claim 6 and further including means for
enabling and disabling said oscillator means to thereby determine
the charging time of said storage capacitor.
8. The apparatus as in claim 5 wherein said means for periodically
applying an ionizing potential to said control terminal of said
xenon flash lamp comprises:
(a) a free-running multi-vibrator for producing trigger pulses at a
predetermined rate;
(b) means for applying said trigger pulses to said control terminal
of said xenon flash lamp, said trigger pulse applying means being
coupled to said means for sensing such that said trigger pulse
applying means produces said trigger pulses only when the amplitude
of said high voltage pulses on said fence wire are below said
predetermined threshold for said predetermined time interval.
9. The apparatus as in claim 8 wherein said means for periodically
applying an ionizing potential to said control terminal of said
xenon flash lamp comprises:
(a) a step-up auto-transformer having a primary winding and a
secondary winding;
(b) a silicon controlled rectifier having an input electrode, an
output electrode and a gate electrode, said input and output
electrode being connected in series with said primary winding and
said secondary winding of said auto-transformer between said
control terminal of said xenon flash lamp and a point of fixed
potential;
(c) a series-connected resistor and capacitor connected between
said battery-operated means and said point of fixed potential and
having the common terminal of said series-connected resistor and
capacitor connected to the common terminal of said primary winding
and secondary winding of said auto-transformer; and
(d) means coupling the gate electrode of said silicon controlled
rectifier to receive said trigger pulses from said free-running
multi-vibrator.
10. The apparatus as in claim 2 and further including a sealed
housing adapted for connection to one of said posts for containing
said sensing means and said xenon flash lamp means, said housing
including a transparent window optically aligned with said xenon
flash lamp for permitting the transmission of light beyond said
housing while shielding said apparatus from the elements.
11. The apparatus as in claim 5 and further including a sealed
housing adapted for connection to at least one of said posts for
containing said xenon flash lamp, said storage capacitor, said
battery-operated means and said means for applying said ionizing
potential, said housing including a transparent window optically
aligned with said xenon flash lamp for permitting the transmission
of light beyond said housing while shielding the contents from the
elements.
12. The apparatus as in claim 1 wherein said appliance is an
electric fence.
13. The apparatus as in claim 1 wherein said appliance is an
electric motor.
14. The apparatus as in claim 1 wherein said sensing means
comprises:
(a) a full-wave bridge rectifier having a pair of input terminals
for coupling said full-wave bridge rectifier to said voltage supply
and a pair of output terminals;
(b) adjustable gain amplifier means for setting the sensitivity of
said sensing means coupled to said pair of output terminals;
and
(c) comparator means for comparing the output from said amplifier
means to a predetermined threshold reference potential.
15. The apparatus as in claim 14 wherein said sensing means further
includes:
(a) timing means coupled to receive the output of said comparator
means for providing a control signal when said output of said
comparator means remains below said threshold reference potential
for a predetermined time interval.
16. The apparatus as in claim 15 and further including:
(a) flash frequency and charge time circuit means controlled by
said control signal for repetitively charging and discharging said
xenon flash lamp means.
Description
BACKGROUND OF THE INVENTION
I. Field of the Invention
This invention relates generally to signalling apparatus, and more
particularly to a device attachable to an electric appliance for
providing a visual signal to a farmer or rancher that the appliance
is not properly operating, the signal being visible from great
distances.
II. Discussion of the Prior Art
While the present invention finds many applications on a farm or
ranch where various electrically operated devices are used and a
fault condition must be signaled so that effective and prompt
attention can be applied, it will be described as applied to use
with electric fence systems. It is to be understood, however, that
the device can find wide usage on a farm or ranch to signal failure
of confinement barns ventilation systems, motor-driven pumps for
irrigation and/or stock watering systems, etc. Electric fences have
long been used to confine animals, such as horses, cattle, sheep
and hogs. The principles of operation of such fences are well
known. High voltage impulses of a predetermined duty cycle are
applied from a fence generator to one or more fence wires which are
strung between posts or insulators so as to define the perimeter of
the field or pasture in which the animals are to be confined. When
an animal brushes against the energized wire, a path to ground is
established through the animal and an uncomfortable shock is
delivered. The animals learn quickly that if they are to avoid
being shocked, they may not touch the fence and, accordingly, they
tend not to break through the fence to roam in undesired areas.
Conditions can arise that may cause the electric fence to
malfunction. For example, a branch may fall from a tree and come to
rest against the fence so as to create a short circuit to ground
through the branch. Similarly, wet grass can grow up to a height
where it, too, significantly decreases the amplitude of the voltage
pulses traversing the fence line so that they may no longer deter
the grazing animals from knocking the fence down or breaking
through it. Malfunction can also occur if an animal such a deer
breaks the electric fence wire. It is important when such
conditions arise that the farmer or rancher be apprised of the
malfunction so that corrective action can be taken before the
animals can stray.
Geoffrey Begg U.S. Pat. No. 4,523,187 describes a monitoring system
for an electric fence which includes a voltmeter for sensing the
voltage of the pulses on the fence and an ammeter for sensing the
current level flowing through the fence wire. If the voltage drops
significantly or the current level increases, a short circuit
condition is detected. Likewise, if the current flow read by the
ammeter drops to zero, an open circuit condition is indicated. The
monitoring system of the Begg patent is physically disposed
proximate the pulse generator used to energize the fence and is
designed to give, by means of a meter reading, an indication of the
voltage level at the far end of the fence. When the signal levels
fall outside of a predetermined threshold setting, an audible alarm
18 is operated. The device of the Begg patent is deficient in that
it does not provide an indication of the location along the fence
line where the fault has occurred which, of course, makes
troubleshooting the fence line more difficult.
The McCutchan et al. U.S. Pat. No. 4,297,633 describes an electric
fence monitoring system in which a plurality of remotely located
responders are operatively coupled to the electric fence for
providing responses back to a receiver located at the site of the
fence generator. If there is a break in the fence wire, the
responder cannot, within a predetermined time interval, deliver its
response signal upon receipt of a fence energizing pulse and,
accordingly, an alarm is indicated at the receiver site.
Another fairly simple electric fence monitoring system is described
in the Pope et al. U.S. Pat. No. 4,220,949. It includes a monitor
circuit, including a relay, at the end of the fence opposite from
the fence-charging circuit. In the event of a break, the relay
switches its contacts to couple an alarm into circuit with a power
supply. The device of the Pope et al. patent is incapable of
indicating to the farmer or rancher the approximate location where
the fault in the fence has occurred. Again, this compounds the
effort in making appropriate repairs.
OBJECTS
It is accordingly a principal object of the present invention to
provide an improved monitoring and indicating system for use with
electrical appliances such as electric fences, ventilating fans,
water pumps, portable generators, etc.
Another object of the invention is to provide an electric fence
monitoring system which is capable of providing an indication of
where along several miles of fencing a fault condition has
developed.
Still another object of the invention is to provide an electric
appliance monitoring and indicating system that provides a visual
indication of a fault condition that can be seen from great
distances.
A still further object of the invention is to provide a low-cost,
yet highly effective appliance fence monitor/indicator that will
remain operational over prolonged periods of time when energized by
a self-contained battery-type power supply.
SUMMARY OF THE INVENTION
In accordance with the present invention there is provided an
apparatus for visually signaling the malfunctioning of an electric
appliance. As applied to an electric fence, a plurality of
monitoring devices are affixed to selected fence posts spaced
considerable distances apart along the fence line for sensing when
the amplitude of the high voltage pulses applied to the fence have
fallen below a predetermined threshold. Also included is a xenon
flash lamp circuit which is coupled to the above-described sensor
and which provides an intense flash of light, visible at great
distances, at predetermined intervals so long as the amplitude of
the high voltage pulses used to energize the fence remain below the
predetermined threshold. To conserve battery power, the xenon flash
lamp circuit can be set to flash at a pre-established frequency
and, similarly, the amount of charging current supplied to the
storage capacitors associated with the xenon lamp is also a
controllable parameter.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing features, objects and advantages of the invention
will become apparent to those skilled in the art from the following
detailed description of the preferred embodiment, especially when
considered in conjunction with the accompanying drawings in which
like numerals in the several views refer to corresponding
parts.
FIG. 1 illustrates a section of a fence line showing the apparatus
of the present invention in place on one of the fence posts;
FIG. 2 is a side elevational view of the housing which is partially
broken away to reveal the disposition of the electronic circuitry
comprising the present invention;
FIG. 3 is a end view of the housing of FIG. 2 showing the window
configuration;
FIG. 4 is a schematic electrical diagram of the circuitry
comprising the preferred embodiment of the present invention;
and
FIG. 5 is a schematic electrical diagram of an alternative
embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIG. 1, there is shown a section of an electric
fence 10 with which the present invention finds use. It comprises a
plurality of regularly spaced posts 12, and extending between the
posts and attached thereto may be strands of barbed wire as at 14.
Mounted on the posts 12 are a plurality of conventional insulating
stand-offs 16 about which is strung a continuous length of wire
18.
The wire 18 is typically connected to the high voltage output of a
fence generator (not shown) and the other output terminal of the
fence generator is connected to ground, via a water pipe or other
type of grounding stake.
With no limitation intended, the fence generator will typically
produce high voltage pulses having an amplitude of 500 to 10,000
volts dc, a duration of from 150 microseconds to 16 milliseconds,
and a pulse repetition rate of 1 Hz. As such, a farm animal coming
in contact with the electric fence wire 18 and whose feet are in
good electrical contact with the ground will receive an
uncomfortable, but non-lethal shock.
The monitoring and indicating device of the present invention is
indicated generally by numeral 20 and is appropriately attached to
one of the fence posts 12. It is directed so that the flash
emanating therefrom is most likely to be seen. As will be explained
in further detail when the schematic diagram of FIG. 4 is
explained, the monitoring and indicating device 20 has one lead
thereof 22 coupled or attached to the fence wire 18 and another
lead thereof connected to ground. If a metal post 12 is employed, a
good ground connection can be made directly to that post. However,
if the posts 12 are of wood, it is usually necessary to ground the
lead 24 using a metal grounding stake 26 or the like.
FIG. 2 illustrates in greater detail the mechanical construction of
the preferred embodiment. It is seen to comprise a tubular housing
28 in which the electrical components are sealed from the elements.
In constructing a prototype of the invention, I found it expedient
to use a Tee fitting, made of PVC plastic normally used for
plumbing purposes. The housing 28 has an integrally formed flange
30 and 32 at opposed ends, respectively, and fitted through the
open end of the T-fitting is 6 volt lantern battery 32 having
spring-type terminals 34 and 36. A threaded PVC plug 38 is designed
to fit into the threaded flange 3 to thereby seal that end of the
housing. The plug 38 may be removed whenever it becomes necessary
to replace the battery 32.
Conveniently fitting into the stem portion 40 of the T-shaped
housing is a storage capacitor 42 having terminals 44 and 46 which
are connected by wires 48 and 50 to appropriate terminals on a
printed circuit board 52. The pc board is appropriately supported
within the housing and is populated with the various electronic
components used in implementing the circuits shown schematically in
FIG. 4. Also appropriately mounted within the housing 28 is a
reflector 54 in which is supported a xenon flash lamp 56.
With reference to the end view of FIG. 3, an opaque plate 58 is
disposed within the flange 32 and is sealed about the perimeter. It
includes a transparent window 60 with which the flash tube 56 and
the reflector 54 are optically aligned. When the xenon flash lamp
56 is excited, a bright flash of light, visible for miles, emanates
the window 60.
Having described the mechanical construction of the preferred
embodiment, consideration will next be given to its electrical
makeup and, in this regard, reference is made now to FIG. 4. The
circuit can conveniently be partitioned into a number of discrete
functional units which are shown as being enclosed by broken line
boxes. Specifically, the circuit comprises a fence pick-up device
62, a missing pulse detector 64, a flash power "sleep" timer 66, a
flash frequency setting circuit 68 and a flash power supply circuit
70.
Alternative ways are illustrated for implementing the fence pickup
device 62. Specifically, it may be an inductive pickup in which a
coil 72 is closely linked to the fence wire 18 (FIG. 1) so that as
high voltage pulses traverse the fence wire, a voltage signal will
be induced in the coil 72. Alternatively, and preferably, the fence
pickup may comprise a resistive voltage divider including a
plurality of series-connected resistors R.sub.1 through R.sub.5,
that divider being connected between the fence line 18 and ground.
Depending upon which set of contacts associated with the voltage
divider are connected together by a jumper 74, the fence voltage
threshold at which the device of the present invention will be
triggered can be set. The six volt lantern battery 32 is used to
provide two separate voltages for operating the circuit of the
present invention. One voltage labeled V.sub.cc will be six volts,
assuming the battery 32 is fully charged. A voltage dropping diode
76 and the capacitor 78 are used to provide a three volt source
required by certain of the integrated circuits yet to be described.
A zener diode 80 is used to eliminate high voltage spikes and other
transient signals from damaging the electronic circuitry by
providing a low impedance path to ground for such signals when the
threshold of the zener diode 80 is exceeded. In a like fashion, the
zener diode 82 performs the same function when an inductive pickup
72 is employed.
Irrespective of the type of pickup employed, the signal developed
thereby is coupled through a capacitor 84 and a resistor 86 to the
input of an invertor 88. The output of the invertor 88 goes to the
missing pulse detector circuit 64. This missing pulse detector
includes a Type LM 555 timer circuit 90 whose trigger input is
connected directly to the output of the invertor 88. A RC charging
circuit is connected between the V.sub.cc source and includes a
resistor 92 and a capacitor 94. The capacitor 94 is shunted by a
PNP transistor 96 whose base electrode is coupled through a
resistor 98 to the output of the invertor 88. The threshold input
terminal of the LM 555 timer circuit 90 is connected to the
junction point 100 between the resistor 92 and the capacitor 94.
Hence, as the capacitor 94 begins to charge through resistor 92, a
point will be reached where the threshold will be exceeded,
provided the charge on the capacitor is not shorted to ground
through the transistor 96. It can be seen, then, that so long as
the high voltage pulses on the fence are occurring at a
predetermined rate, the threshold for the timer 90 will not be
exceeded. However, if something should happen that fence pulses are
missing or of an insufficient amplitude, the transistor 96 will not
be turned on to short out the capacitor 94 and it will charge to
the point where the threshold for the timing circuit is exceeded
and the output of the timer circuit 90 shifts its binary state.
When operating in the monitoring mode, the output of the timer 90
is connected by means of conductor 102, a jumper 104, a conductor
106 and a conductor 108 to the reset input of a further LM 555
timer 110 configured to operate as a one shot. It comprises the
flash power "sleep" timer 66. The period for the one-shot is
established by the RC timing circuit including the resistor 112 and
the capacitor 114. So long as the missing pulse detector circuit 64
is not detecting the absence of appropriate amplitude fence voltage
pulses, the reset will be maintained on the one-shot 110. Likewise,
the reset will be maintained on yet another LM 555 timer, this time
configured as a multi-vibrator 116. It comprises the flash
frequency circuit 68. The frequency of the output from the
multi-vibrator 116 is determined by the magnitude of the resistor
118 and the capacitor 120. By properly choosing these values, the
xenon lamp may be made to flash at 30-second intervals, one-minute
intervals or any other frequency, it being recognized that if the
flashing is too infrequent it may go unnoticed but that too
frequent flashing consumes battery charge.
The output of the flash frequency multi-vibrator 116 is connected
via conductor 122 and the differentiating circuit including
resistor 124 and capacitor 126 to the input of an invertor 128. The
output of this invertor is connected to the trigger input of the
one-shot circuit 110 in the flash power sleep timer 66.
The output from the one-shot 110 is applied over conductor 130 to
the reset input of still another LM 555 timer configured as a
free-running oscillator 132 which forms part of the flash power
supply 70. The frequency of oscillation of the output from the
free-running oscillator 132 is determined by the RC timing circuit
including resistor 134 and capacitor 136. The signal output of
oscillator 132 is used to drive a FET switch 138 which is connected
in series circuit with the primary winding of a step-up transformer
140 between the voltage source V.sub.cc and ground. Thus, the
oscillator and FET switch function as a chopper for the dc voltage
and creates an alternating current signal that can be stepped-up by
the transformer 140. The secondary winding of the transformer 140
is connected in series with a half-wave rectifying diode 142 and
the main storage capacitor 42 for the xenon flash lamp 56. Thus, a
high voltage direct current becomes available for charging that
capacitor.
The storage capacitor 42 is connected directly in parallel with the
main power electrodes of the xenon flash lamp 56 but the charge
stored on that capacitor cannot be dumped through the xenon flash
lamp 56 to cause it to flash until the xenon gas is appropriately
ionized.
From what has been thus far described, it should be readily
apparent that the circuit 66 determines the length of time that the
flash power supply is operative to charge the main storage
capacitor 42. In this way, battery power is conserved. That is to
say, charging current is not continuously provided to the main
storage capacitor 42 but instead is only charged for a period of
time determined by the circuit 66 and then, only when the missing
pulse detector 64 is detecting a fault condition on the fence so as
to actuate the flash frequency circuit 68.
The output from the flash frequency multi-vibrator 116 is applied
through an invertor 144, a coupling capacitor 146, a diode 150 and
a pair of buffer invertors 152 and 154 and a current limiting
resistor 156 to the gate electrode of a silicon-controlled
rectifier semi-conductor switching device 158. The SCR is coupled
in series with a step-up auto-transformer 160 having a primary
winding 162 and a secondary winding 164 series connected to the
trigger electrode 166 of the xenon flash tube 56. A RC charging
circuit including resistor 168 and capacitor 170 is connected to
the common terminal 172 of the primary winding 162 and the
secondary winding 164. Capacitor 170 becomes charged by the
rectified alternating current developed across the secondary of the
step-up transformer 140 and when the SCR 158 is turned on, the
capacitor 170 discharges rapidly through the primary winding 162 of
the auto-transformer 170 through the SCR 158 to ground. The rapid
current surge through the primary winding 162 induces a high
voltage onto the secondary winding 164 of the transformer and this
voltage is sufficient to cause ionization of the xenon gas within
the flash tube 56. Once the gas is ionized, it becomes a low
impedance allowing the main storage capacitor 42 to dump its charge
through the xenon flash tube, resulting in a brilliant, short flash
of light being emitted therefrom. In daylight, the flash can be
seen for a mile or more and at night for up to 6 miles.
Summarizing the operation of the circuit of FIG. 4, the Type 555
timer 90 in the missing pulse detector 64 is normally precluded
from issuing an output on its "out" terminal so long as the charge
on the capacitor 94 never reaches the threshold voltage for the
timer. Capacitor 94 charges through resistor 92, but is discharged
each time transistor 96 is turned on by the fence voltage pulses.
If the fence voltage falls below the threshold voltage established
by the jumper 74 on the voltage divider R.sub.2 through R.sub.5,
transistor 96 will not turn on and, hence, the threshold voltage
for the timer 90 will be exceeded as the charge builds up on
capacitor 94.
When the timer 90 outputs a pulse, it triggers the one-shot 110 in
the flash power "sleep" timer 66 and the period of that one-shot
determines the charge time of the large storage capacitor 42. The
period is determined by the RC timing circuit including resistor
112 and capacitor 114. In particular the output of the one-shot 110
enables the free-running oscillator 132 which switches the FET 138
on and Off to chop the battery current flowing in the primary of
the step-up transformer 140. The resulting high AC voltage is
half-wave rectified by the diode 142 and is applied to the main
storage capacitor 42 and to the capacitor 170 through the resistor
168 to build up a charge thereon. When the one-shot 110 times out,
the charging ceases.
Assuming that the sense power on/off jumper 104 is in its "off"
position, such that the xenon lamp can flash when the fence power
fails or falls below a threshold set by the input voltage divider,
the output of the missing pulse detector 64 removes the reset from
the free-running multi-vibrator 116 of the flash frequency circuit
68 and it produces trigger pulses which are applied, via diode 150
and the buffer invertors 152 and 154, to the gate electrode of the
SCR 158. This causes capacitor 170 to discharge through the primary
winding 162 of the step-up auto-transformer 160 to produce a
voltage of approximately 5 KV across its secondary, that voltage
being sufficient to trigger the xenon lamp 56. Once the gas in the
lamp is ionized by that trigger input, it constitutes a low
impedance path across the main storage capacitor 42 and it rapidly
discharges through the xenon lamp, causing it to brilliantly
flash.
When trouble-shooting a fence to see where the problem is, one can
carry the device of FIG. 2 but with the sense-power on/off jumper
reversed from that shown in FIG. 4 such that the output from the
555 timer is inverted by invertor 174 before being applied to the
reset inputs of the one-shot 110 and the multi-vibrator 116. This
will result in flashes being emitted when fence pulses are present
rather than when absent. The user may walk along the fence line,
periodically clipping the leads of the device between the fence
wire and ground and so long as a flash is produced, the user will
know that the fence is operational between the location of the
fence energizing generator and the point at which the test is being
made. If the unit fails to flash, it is known that a low impedance
path, such as a tall wet grass, a broken branch or some similar
object is contacting the fence ahead of the location at which the
test is being made.
ALTERNATIVE EMBODIMENT
FIG. 5 illustrates an alternative circuit arrangement for
implementing the electric appliance fault monitor and indicating
system of the present invention. While the first embodiment
disclosed herein has been described in connection with the
monitoring and indicating of faults in an electric fence at great
distances, to illustrate the versatility of the present invention,
the embodiment shown in FIG. 5 will be described as applied to
monitoring the power to a 220 volt ventilating fan system commonly
used in poultry barns to prevent over-heating of the animals.
Failure of such ventilating fans without relatively prompt
corrective action can result in the death of thousands of
birds.
The power sense bridge shown enclosed by dash line box 200 allows
the circuit of the embodiment of FIG. 5 to be used with either ac,
dc+ or dc-voltages. In this application, the device of FIG. 2 is
mounted on the exterior of the barn, preferably on its roof so that
the flash produced can be observed from a considerable distance.
The input voltage to be monitored is connected across the terminals
202 and 204 and through a resistor 206 to a first input of a full
wave diode rectifier bridge 208. The common terminal 204 connects
to the other power input terminal of that bridge. Irrespective of
whether the applied voltage to the terminals 202 and 204 is dc or
ac, a dc voltage will be developed across the load resistor 210.
This voltage is also applied to the non-inverting input of an
operational amplifier 212 which may, for example, be a Type LM 2902
integrated circuit having a feedback path including a plurality of
gain adjusting resistors, one or more of which can be selected for
insertion into the feedback path by operation of selected ones of
the plural single-pole, single-throw switches 216. By appropriate
selection of the feedback resistor, the device of the present
invention can be made to operate with a power source ranging from,
for example, 5,000 volts down to 100 volts. This, of course, adds
to the versatility of the monitoring and indicating device.
The sensitivity select circuit 211 also includes an integrated
circuit operational amplifier configured as a voltage comparator
218. The voltage developed at the output of the adjustable gain
amplifier 212 is applied to the non-inverting input of the voltage
comparator 218 while a reference potential of approximately 2.7
volts is applied to the inverting input thereof. So long as the
power sensing bridge and sensitivity select circuit are detecting a
voltage in excess of the value selected by operation of one or more
of the switches 216, the output of the voltage comparator 218 will
be high. This signal is coupled, via a resistor 220, to the base
electrode of NPN transistor 222 whose emitter electrode is
connected to ground and whose collector electrode is coupled to a
junction point 224 between a resistor 226, a capacitor 228 and the
non-inverting input of an operational amplifier 230. The inverting
input of the amplifier 230 is connected to the common junction 232
between a pair of series connected resistors 234 and 236 which are
themselves connected between a source of positive potential (+5
volts) and ground. So long as the voltage being monitored remains
above the threshold level established, the NPN transistor 222 will
remain conducting due to the high output from the voltage
comparator 21B. With the transistor 222 conducting, the capacitor
228 connected between the transistors collector and emitter cannot
become charged and the signal at the junction 224 remains low. If,
however, the voltage being monitored falls below the prescribed
level, the output from the voltage comparator 218 will go low,
turning off the transistor 222 and permitting the capacitor 228 to
charge up. When the charge on the capacitor causes the voltage at
junction 224 to exceed the threshold applied to the inverting input
of the operational amplifier 230, its output will go high. Thus,
the circuitry shown enclosed by the broken line box 238 functions
much like the missing pulse detector in the circuit of FIG. 4.
The flash frequency and charge time oscillator is shown enclosed by
broken line box 240 and it includes a low frequency oscillator,
indicated generally by numeral 242, whose duty cycle is established
by the resistors 244 and 246 and the capacitor 248. The common
junction between the series-connected resistors 244 and 246 is tied
to the non-inverting input of an operational amplifier 250 having a
feedback resistor 252 connected between its output junction 254 and
the non-inverting input. Likewise, a resistor 256 is connected
between the junction 254 and the inverting input of the amplifier
250. A capacitor 258 couples the inverting input to ground. The
component values of the resistor 256 and the capacitor 258
determine the frequency of oscillation of the charge time
oscillator. Typically, those values may be set so that the
oscillator operates at a frequency of approximately one cycle per
minute although it may be made to oscillate at a higher or lower
rate by merely adjusting those components.
The output from the oscillator appearing at junction 254 is coupled
through a resistor 260 to the base electrode of a further NPN
transistor 262. The emitter electrode of that transistor is
connected to ground and the coil 264 of a single-pole, double-throw
relay 266 is connected between a source of positive potential,
V.sub.cc, at terminal 268 and the collector electrode of transistor
262. A half-wave diode rectifier 270 is connected in parallel with
the relay coil 264.
The normally closed contact labeled "NC" is connected by a
conductor 272, a diode 274 and a resistor 276 to the gate electrode
of a SCR 278. The gate electrode is also coupled through a parallel
combination of a resistor 280 and a capacitor 282 to a bus 284 in
the flash power supply circuit shown enclosed by broken line box
286. The normally open contact of the relay 266 is coupled to the
voltage supply 268 and when the switch ar 267 of that relay
switches to the normally open position, that potential is applied,
via conductor 288, to the flash power supply 286. In particular,
the conductor 288 connects to a junction point 290 to which one
terminal of the primary winding 292 of a step-up transformer 294 is
connected. The other terminal of the primary winding is connected
to the collector electrode of a NPN transistor 296 whose collector
electrode is grounded at junction 298. A capacitor 300 is also
connected between the junctions 290 and 298.
The base electrode of transistor 296 is connected by a capacitor
302 to ground and by a conductor 304 to a tap 306 on the secondary
winding 308 of the step-up transformer 294. A resistor 310 and a
diode 312 couple the bus 284 to one side of the secondary winding
308 while the other side of that winding is connected through a
resistor 314 to the conductor 388. The main storage capacitor for
the flash power supply 286 is identified by numeral 316 and it is
connected directly in parallel with the terminals of a xenon flash
lamp 318 and between the conductor 288 and the bus 284. The trigger
terminal for the xenon lamp 318 is connected to an output terminal
of a step-up transformer 320. The transformer 320 is configured as
an autotransformer and its primary winding 322 is connected in
series between the conductor 288 and the SCR 278 to the bus
284.
The voltage V.sub.cc is available from a six volt battery connected
between the battery terminals 324 and 326. To provide the five volt
supply voltage required for the integrated circuits employed, a
diode 328 provides the voltage dropping function. The capacitors
330 and 334 which are connected in parallel between ground and the
five volt supply provide temporary voltage to the threshold
determining circuit 217 in the sensitivity select network 211 and
to the missing pulse detector 238 during those time intervals when
the main storage capacitor 316 for the xenon lamp 318 is being
charged following a flash. The changing current places a heavy load
on the battery, dropping its voltage, thus making it necessary to
temporarily provide the necessary bias potentials from capacitors
330 and 334.
Having described the construction of the alternative embodiment of
FIG. 5, consideration will next be given to its mode of operation.
As mentioned previously, so long as the proper voltage for the
appliance being monitored is being applied across the terminals 202
and 204, the output from the comparator 218 will be high, forcing a
low signal at the output of the operational amplifier 230 in the
missing pulse detector. This low signal prevents the oscillator 242
from oscillating causing a low signal to be applied to the base of
the transistor 262. This low signal renders that transistor
non-conducting and, hence, no power will be applied to the flash
power supply circuit 286.
If now, however, the voltage for the appliance, here assumed to be
a 220 volt motor-driven ventilating fan, the output of the voltage
comparator 218 will go low turning the transistor 222 off. With
transistor 222 non-conducting, a charging current flows through the
capacitor 228 causing the voltage at junction 224 to rise
asymptotically until the voltage applied to the non-inverting input
of the operational amplifier 230 exceeds the threshold applied to
its inverting input, via the voltage divider including resistors
234 and 236. When this happens, the output of circuit 230 goes
high, as does the output from the oscillator 242 at junction 254.
With the voltage at junction 254 high, transistor 262 is turn.RTM.d
on, thereby drawing an energizing current through the relay coil
264 from the supply connected at terminal 268. This action causes
the switch arm 267 to move to the normally open contact "NO" such
that the voltage V.sub.cc is applied over line 288 to the flash
power supply 286. The approximately six volt dc voltage, applied
via conductor 288, energizes the blocking oscillator including the
transistor 296 and the step-up transformer 294, producing an
approximately 300 volt potential across the secondary winding 308
of that transformer. That ac potential is half-wave rectified by
the diode 312 and the resulting dc current is used to charge the
main storage capacitor 316 for the xenon flash lamp 318.
The lamp does not flash at this time in that no trigger pulse is
applied to the xenon lamp to create the necessary ionization
potential for the xenon gas within the flash tube. When the
oscillator 242 in the "flash frequency and charge time oscillator"
circuit 240 again switches low, the transistor 262 will again be
turned off, de-energizing the relay coil 264 and causing the switch
arm 267 to again move to the normally closed, "NC", contact. This
effectively connects the gate electrode of the SCR 278 to the bus
288, discharging the capacitor 289 through the diode 274 and the
current limiting resistor 276 to thereby switch the SCR 278 to its
conducting state. With SCR 278 conducting, a rush of current flows
through the primary winding 322 thereof, causing a high voltage
pulse to be generated across the secondary winding 320 triggering
the flash tube 318. Once the gas in the flash tube 318 is ionized,
it provides a low impedance path for a discharge of the main
storage capacitor 316 producing the bright flash. So long as the
fault condition prevails, the oscillator 242 will continue to cycle
in the fashion already indicated with charging and flashing taking
place on alternate half cycles its output.
This invention has been described herein in considerable detail in
order to comply with the Patent Statutes and to provide those
skilled in the art with the information needed to apply the novel
principles and to construct and use such specialized components as
are required. However, it is to be understood that the invention
can be carried out by specifically different equipment and devices,
and that various modifications, both as to the equipment details
and operating procedures, can be accomplished without departing
from the scope of the invention itself.
* * * * *